A magnetron sputtering apparatus used in a manufacturing process of semiconductor devices, for example, as shown in FIG. 13, is configured such that a target 13 made of a film forming material is disposed to face a substrate 12 in a vacuum chamber 11 set to a low pressure atmosphere, a magnet body 14 is provided at the top side of the target 13, and, if the target 13 is a conductor such as a metal, a magnetic field is generated in the vicinity of a bottom surface of the target 13 in a state where a negative DC voltage is applied thereto. Further, there is provided an anti-adhesion shield (not shown) to prevent the adhesion of particles to an inner wall of the vacuum chamber 11.
The magnet body 14, as shown in FIG. 14, generally configured such that, for example, a circular magnet 16 having a polarity different from that of an annular magnet 15 is disposed on the inside of the magnet 15. FIG. 14 is a plan view of the magnet body 14 seen from the target 13. In this example, the polarity of the outer magnet 15 facing the target 13 is set to an S pole and the polarity of the inner magnet 16 facing the target 13 is set to an N pole. Accordingly, in the vicinity of the bottom surface of the target 13, a horizontal magnetic field is formed by cusp magnetic fields based on the outer magnet 15 and the inner magnet 16.
When a negative DC current is applied to the target 13 from a DC power supply unit 19 while introducing an inert gas such as Ar gas or the like into the vacuum chamber 11, the Ar gas is ionized by the electric field to generate electrons. The electrons are drifted by the horizontal magnetic field and the electric field, thereby generating a high-density plasma. Then, the target 13 is sputtered by Ar ions in the plasma, so that metal particles are released from the target 13 and deposition is performed on the substrate 12 by the released metal particles.
With such a mechanism, as shown in FIG. 15, on the bottom surface of the target 13, an annular erosion 17 is formed according to the array of magnets immediately below a middle portion between the outer magnet 15 and the inner magnet 16. In this case, the magnet body 14 is rotated to form the erosion 17 on the entire surface of the target 13. However, in the above-described array of the magnets, it is difficult to uniformly form the erosion 17 in a radial direction of the target 13.
Meanwhile, the in-substrate distribution of the deposition rate depends on the intensity (magnitude of sputtering rate) of the erosion 17 on the surface of the target 13. Therefore, if the uniformity of the erosion 17 is poor as described above, in the case of reducing a distance between the target 13 and the substrate 12 as shown by a dotted line in FIG. 15, the shape of the erosion is reflected as it is, and the in-substrate distribution of the deposition rate is deteriorated. For this reason, conventionally, a sputtering process is performed by setting a distance between the target 13 and the substrate 12 in a range from about 50 mm to 100 mm.
In this case, the particles released from the target 13 by the sputtering are scattered to the outside, so that, if the target 13 is separated from the substrate 12, the amount of sputtered particles adhering to the anti-adhesion shield becomes greater, and the deposition rate at an outer peripheral portion of the substrate is decreased. Therefore, the in-substrate uniformity of the deposition rate is generally ensured by making the erosion of the outer periphery deep, i.e., by increasing the sputtering rate of the outer periphery. However, as described above, in this configuration, since the amount of sputtered particles adhering to the anti-adhesion shield becomes greater, the deposition efficiency is as low as about 10% and a high deposition rate cannot be obtained.
The target 13 needs to be exchanged immediately before the erosion 17 reaches the bottom surface of the target 13.
However, as previously described, if the in-plane uniformity of the erosion 17 is low and there locally exists a site where the progress of erosion is rapid, the utilization efficiency of the target 13 drops to about 40% since the time of replacing the target 13 is determined in accordance with the site. In order to reduce the manufacturing cost and enhance the productivity, it is also necessary to increase the utilization efficiency of the target 13.
Recently, a tungsten (W) film has been recognized as a wiring material for memory devices, and it has been suggested to form a film at a deposition rate of, e.g., about 300 nm/min. In the above-described configuration, it is possible to ensure the deposition rate by increasing the application power to, e.g., about 15 kWh. However, the mechanism becomes complex and the operation rate declines. The manufacturing cost also increases.
Here, in order to ensure the in-plane uniformity of the deposition rate, the in-plane uniformity of the erosion needs to be improved. To do so, it is considered to dispose a plurality of magnets in a planar form. Japanese Patent Application Publication No. 2004-162138 suggests a configuration in which a plurality of magnets having different polarities are alternately arranged equidistantly between any two magnets in a planar form facing the target to generate a point cusp magnetic field below the target.
Further, Japanese Patent Application Publication No. 2000-309867 suggests a technique in which a plurality of magnets each having a central axis parallel to the surface of the target is arranged such that the central axes are substantially in parallel to each other and N poles and S poles of the magnets face each other in a direction substantially perpendicular to the central axes.
In the above arrangement of the magnets, in order to increase the deposition rate, the strength of the magnetic field is increased by reducing the distance between the magnets or increasing the surface magnetic flux density. However, this causes the increase in the repulsion of the magnetic flux and the magnetic flux line to be distorted. Further, an area where a horizontal magnetic field is obtained is decreased. The above-cited references do not disclose an arrangement of magnets through which a horizontal magnetic field is generated in a wide range. Thus, it is difficult to realize the object of the present invention in which the high speed film formation is obtained while ensuring the in-plane uniformity of the deposition rate.